1. Field of the Invention
This invention relates to a reel spring structure for a video tape cassette.
2. Description of the prior Art
Generally, referring to FIGS. 1-3 a reel spring for a video tape cassette is secured to the inner surface of an upper case section 10 of the cassette, as shown in FIG. 1, and functions to support shafts 12 (FIG. 3) of tape reels on which a video tape is wound, such that in an assembled state of the upper case section 10 and a lower case section 11 (FIG. 2), the tape reel shafts can be smoothly rotated within the cassette.
A prior art reel spring as shown in FIGS. 6 and 7 of the accompanying drawings is disclosed in U.S. Pat. No. 4,770,367. The reel spring is in the form of an elongated strip of constant width (greater than 8 mm) and has a central portion 13 in which is formed a pair of holes 13a for attaching of the spring to the case, and slightly inclined portions 14 at the opposite ends of the central portion 13. Therefore, the reel spring 15 is of a wing-like shape in its overall configuration.
This prior reel spring supports the shafts so that the video tape reels may be smoothly rotated due to the resiliency of the spring per se and the supporting force generated by the inclined portions 14. However, the resiliency of the spring is reduced after a given period of time due to an excessive variation in the tension of the reel spring, so that the spring may lose the necessary supporting force for the tape reel shafts. Therefore, to overcome this, the spring is generally formed to have a width which is greater than 8 mm.
This, however, requires a large quantity of raw material, resulting in a higher manufacturing cost.